user = {
      age: '123'
  }
  aa = user.age
  Object.defineProperty(user, "age", {
      get: function () {
          return aa
      },

      set: function (newVal) {
          console.log("这个人来设置值了！！");
          aa = newVal
      }
  })
  console.log(user.age)
  user.age = '23342'
  console.log(user.age)